If you are running 2.0.6 and would like only the changed files, you can download this file:http://www.thecodecave.com/downloads/wp206to207rc2.zip
(Note that this file is relative to your blog directory and not to the root with a wordpress directory underneath it. It contains just three files. So just extract it, with paths to where your blog is installed.)

To test feeds’ 304 Not Modified headers, I recommend getting the Live
HTTP Headers extension for Firefox:

http://livehttpheaders.mozdev.org/

A. Warming up:

1. Make sure that Firefox will display feeds (and not pipe them to
an external RSS viewer)
2. Disable any caching plugins on your site like WP-Cache
3. Upload the 2.0.7 files (no need to run an upgrade)
4. Clear your Firefox cache

B. Testing procedure:

1. Open up Live HTTP Headers (Tools > Live HTTP Headers)
2. Visit http://yoursite.com/wp-rss2.php?test=123
3. Verify that the response header for /wp-rss2.php?test=123 is 200 OK
4. Clear the Live HTTP Headers output
5. Reload the feed
6. Verify that the response header for /wp-rss2.php?test=123 is 304
Not Modified

There should be no conflicting Status: header (that is, any Status
header should match the response code of the main HTTP response header).

NOTE: The ?test=123 part is just to make sure that your first request
isn’t already cached.